No choise between UTM zones when using an AOI

If the AOI lays in an area which is covered by two S2 tiles with different UTM zones it is not possible anymore to choose the projection/UTM zone. It always uses the "smaller" one even though utm_zone parameter is set to the "bigger" one.

How to reproduce:

### overlapping utm meckpomm; force one utm

# config
config = loadConfiguration(path="data/default_config.json")

# adapt config
config["user_settings"]["aoi_settings"]["bounding_box"] = [13.10766141955574, 53.452302211632144,
                                                           13.237473951256504, 53.50549339832173]
config["user_settings"]["aoi_settings"]["date_range"] = ["2018-07-01", "2018-07-10"]
config['user_settings']["tile_settings"]["sentinel:utm_zone"] = {"in": [33]}
config["user_settings"]["aoi_settings"]["apply_SCL_band_mask"] = False
config["user_settings"]["aoi_settings"]["aoi_min_coverage"] = 20

# start download
s2Downloader(config_dict=config)

result:

[INFO ]  Date                      ID                        UTM Zone   EPSG       Valid Cloud Cover    Tile Cloud Cover     Tile Coverage  
[INFO ]  2018-07-08T10:10:25Z      S2A_32UQE_20180708_0_L2A  32         32632      True                 24.4                 44.06          
[INFO ]  2018-07-06T10:20:22Z      S2B_32UQE_20180706_0_L2A  32         32632      True                 25.87                100            
[INFO ]  2018-07-03T10:10:23Z      S2B_32UQE_20180703_0_L2A  32         32632      True                 1.45                 44.12          
[INFO ]  2018-07-01T10:24:04Z      S2A_32UQE_20180701_0_L2A  32         32632      True                 41.3                 100            
[INFO ]  Nonzero pixels: 100.0 %
[INFO ]  Valid pixels: 7.103220961281709 %
[ERROR]  For date 2018-07-08 there is not any available data for the current tile and AOI settings.
[INFO ]  Nonzero pixels: 100.0 %
[INFO ]  Valid pixels: 39.09448709390298 %
[INFO ]  Getting data for: S2B_32UQE_20180706_0_L2A
[INFO ]  Bands to retrieve: ['B01', 'B02', 'B05']
[INFO ]  https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/32/U/QE/2018/7/S2B_32UQE_20180706_0_L2A/B01.tif
[INFO ]  https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/32/U/QE/2018/7/S2B_32UQE_20180706_0_L2A/B02.tif
[INFO ]  https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/32/U/QE/2018/7/S2B_32UQE_20180706_0_L2A/B05.tif
[INFO ]  Nonzero pixels: 100.0 %
[INFO ]  Valid pixels: 86.6050567423231 %
[INFO ]  Getting data for: S2B_32UQE_20180703_0_L2A
[INFO ]  Bands to retrieve: ['B01', 'B02', 'B05']
[INFO ]  https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/32/U/QE/2018/7/S2B_32UQE_20180703_0_L2A/B01.tif
[INFO ]  https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/32/U/QE/2018/7/S2B_32UQE_20180703_0_L2A/B02.tif
[INFO ]  https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/32/U/QE/2018/7/S2B_32UQE_20180703_0_L2A/B05.tif
[INFO ]  Nonzero pixels: 100.0 %
[INFO ]  Valid pixels: 69.77845460614152 %
[INFO ]  Getting data for: S2A_32UQE_20180701_0_L2A
[INFO ]  Bands to retrieve: ['B01', 'B02', 'B05']
[INFO ]  https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/32/U/QE/2018/7/S2A_32UQE_20180701_0_L2A/B01.tif
[INFO ]  https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/32/U/QE/2018/7/S2A_32UQE_20180701_0_L2A/B02.tif
[INFO ]  https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/32/U/QE/2018/7/S2A_32UQE_20180701_0_L2A/B05.tif